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lightning protection
Hi all,
For years I lived in an apartment and just had antenna's in the attic , but now having moved to a house in a few months I'll be putting up a 10-160 wire type antenna in my trees. Given the recent spate of serious thunderstorms, and the accompanying lightning, I'm a bit concerned about properly grouding the antenna so that I don't fry the house *smile*. I know about some articles on the ARRL site, but was wondering if anyone else had some ideas or pointers on how to practically do this ? Jerry |
"Jerseyj" wrote in message ... Hi all, For years I lived in an apartment and just had antenna's in the attic , but now having moved to a house in a few months I'll be putting up a 10-160 wire type antenna in my trees. Given the recent spate of serious thunderstorms, and the accompanying lightning, I'm a bit concerned about properly grouding the antenna so that I don't fry the house *smile*. I know about some articles on the ARRL site, but was wondering if anyone else had some ideas or pointers on how to practically do this ? Jerry Have a look at www.furse.com They used to do a very good pamphlet about lightning and protection. -- Woody harrogate2 at ntlworld dot com |
In article ,
Jerseyj wrote: For years I lived in an apartment and just had antenna's in the attic , but now having moved to a house in a few months I'll be putting up a 10-160 wire type antenna in my trees. Given the recent spate of serious thunderstorms, and the accompanying lightning, I'm a bit concerned about properly grouding the antenna so that I don't fry the house *smile*. That's a very good concern to have! I'd encourage you to consult with a local professional (electrician) who is familar with your local conditions (weather, soil, electrical, and legal). I know about some articles on the ARRL site, but was wondering if anyone else had some ideas or pointers on how to practically do this ? You might find it useful to review the following document: http://www.radagast.org/~dplatt/hamr...-grounding.pdf It's probably got more information than you want or need, but some sections of it could be quite useful in planning your system. Understanding the requirements of your local electrical code (which is probably based in large part on the National Electric Code) would also be a good idea. The text of the NEC isn't available online as far as I know (it's copyrighted) but I understand that most good libraries should have a copy. The basic approach you'd want to take, I believe, is to make sure that the feedline is well grounded immediately before it enters your building. You'll probably want to hammer in a new ground rod at this location, in order to keep the distance between grounding point and ground to a minimum, and if you do so you should/must install a heavy-gauge "bonding" wire between this ground rod and your building's main grounding point (probably at the electrical service entrance). Installing lightning/surge suppressors of one sort or another in the feedline at the grounding point would also be a good idea. They might help shunt away a high-voltage spike, induced by a nearby lighting strike, which could damage your equipment. If your shack is not on the first floor, it'd probably be a good idea for you to run the feedline down the wall to ground level, ground it there, and then run it to the antenna. You might want to consider an arrangement in which the antenna feedline drops down from the feedpoint to ground level, is connected to a ground rod at that point, and then runs along or through the ground to your house (use a "direct bury" coax, in this case, to avoid contamination of the cable by soil moisture and chemicals!). This could help keep direct- or near-direct-strike current away from your house. One of the best things you can do is to have some sort of easy-access connector coupling, located outside the house (e.g. at the grounding block). If a storm seems imminent, or any time you won't be using the rig for a while, disconnect the end of the antenna feedline and toss it away from the house. -- Dave Platt AE6EO Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |
Hi Jerry,
Dave's comments are accurate and helpful, in almost every case. But there is the possibility of a very substantial simplification here. The Key Question: Do you need or want to operate your rig during electrical storms? If the answer is YES, then you better do everything Dave suggests-- and possibly a whole lot more. Praying a little might also be helpful. But if the answer is NO, then you would probably do just fine (with respect to antenna-specific risk) using the last suggestion only: One of the best things you can do is to have some sort of easy-access connector coupling, located outside the house (e.g. at the grounding block). If a storm seems imminent, or any time you won't be using the rig for a while, disconnect the end of the antenna feedline and toss it away from the house. The main thing to remember on this one is that the more CONVENIENT you make your disconnect, the more likely it will be that you'll actually USE it appropriately. 73, Ed, W6LOL |
For a receiving antenna, a coherer provides excellent lightning
protection. Unfortuantly, on a transmitting antenna, the rf would immediately make the coherer conductive and a direct short to ground (perhaps very low QRP power could be used?) One can easily be construted with a bottle filled with metal filings, two bare wires are inserted into the filings (not touching and seperated by a substantial amount of the filings), one wire goes to a good earth ground, the other to the antenna. If the coherer shorts to ground it only needs to be shaken to reset (I would suspect in a real lightning strike the metal would be fused, quite possibly even vaporized.) John "Jerseyj" wrote in message ... Hi all, For years I lived in an apartment and just had antenna's in the attic , but now having moved to a house in a few months I'll be putting up a 10-160 wire type antenna in my trees. Given the recent spate of serious thunderstorms, and the accompanying lightning, I'm a bit concerned about properly grouding the antenna so that I don't fry the house *smile*. I know about some articles on the ARRL site, but was wondering if anyone else had some ideas or pointers on how to practically do this ? Jerry |
On Sun, 17 Jul 2005 08:07:15 -0400, Jerseyj
wrote: Hi all, For years I lived in an apartment and just had antenna's in the attic , but now having moved to a house in a few months I'll be putting up a 10-160 wire type antenna in my trees. I have a 10-80 wire connected between 3 trees. It's fed with ladderline. Lightning protection is simple -- with banana plugs and jacks, I can unplug the ladderline just outside the window whenever it looks rainy. You might think about whether you want to use coax or some kind of balanced line -- balanced line is a simple disconnect. bob k5qwg Given the recent spate of serious thunderstorms, and the accompanying lightning, I'm a bit concerned about properly grouding the antenna so that I don't fry the house *smile*. I know about some articles on the ARRL site, but was wondering if anyone else had some ideas or pointers on how to practically do this ? Jerry |
"Jerseyj" wrote in message ... Hi all, For years I lived in an apartment and just had antenna's in the attic , but now having moved to a house in a few months I'll be putting up a 10-160 wire type antenna in my trees. Given the recent spate of serious thunderstorms, and the accompanying lightning, I'm a bit concerned about properly grouding the antenna so that I don't fry the house *smile*. I know about some articles on the ARRL site, but was wondering if anyone else had some ideas or pointers on how to practically do this ? HI, Good to read : http://www.astrosurf.org/lombry/qsl-...protection.htm Personnaly, in my humble opinion, under thundery weather there is no better solution than unpluging all electronic devices... Thierry, ON4SKY Jerry |
Jerry wrote:
"I know about some articles on the ARRL site, but was wondering if anyone else had some ideas or pointers on how to pratically do this?" Coax helps protect your radio from lightning. It rejects common-mode currents inside which might otherwise damage the radio. Thunderstorms often produce lightning from clouds charged to 100 million volts with respect to the earth. Current may oscilate up to 200 thousand amps in a lightning discharge. Temperature inside the stroke may reach 30 thousand degrees C (5x the temperature of the sun`s surface). A stroke starts and stops abruptly, so it contains r-f in addition to d-c. The discharge may take up to 150 milliseconds and consist of several flashes in both directions. It may include a path miles long, so it has a pretty good ionization trail for an antenna. If your antenna is struck by lightning, it is best to bypass the energy aroundb people and equipment. Medium wave stations have arc-gaps around the tower base insulators, Faraday screens between primary and secondary of tower r-f coupling transformers, and tower lighting chokes which keep both r-f and lightning out of the power mains. High frequency stations often use balanced wire lines, and these have an arc-gap from each wire to the earth at a point outside the station. VHF, UHF, and microwave stations use grounded antennas and coax. Towers which support the antenna generally have each tower leg separately grounded by a heavy cable to its own ground rod near the tower base. R-F cables and waveguide are grounded at the antenna and at least at the base of the tower. Coax nay be coiled with several turns between the tower base and the shack to discourage lightning on the outside of the coax from entry to the shack. Waveguide is solidly bonded to the tower but not usually coiled to make a lightning choke. The solid-state VHF, UHF, or microwave station often needs additional surge protection because of the difference in potential between electric service and antenna system grounds This takes the form of husky r-f chokes in each power wire to the r-f equipment. Each choke is shunted at each end to ground with a capacitor and with a voltage limiting device or devices, often MOV`s. There are ready-made brute force coil and capacitor low-pass pi-filters which need only addition of MOV`s to make them effective lightning suppressors. I made mine in an earlier time using Miller Coil Company tower lighting chokes and they worked well. You could wind 2 or 3 dozen turns of #12 or #14 insulated wire in an 8-in. dia. circle to make your own 0.1 millihenry chokes. The standard choke used to be 2.5 millihenry, but it is not critical. The same wiring techniques required for noise reduction apply to the biggest noise of all, lightning. Best regards, Richard Harrison, KB5WZI |
"Richard Harrison" wrote in message ... Jerry wrote: "I know about some articles on the ARRL site, but was wondering if anyone else had some ideas or pointers on how to pratically do this?" Coax helps protect your radio from lightning. It rejects common-mode currents inside which might otherwise damage the radio. Thunderstorms often produce lightning from clouds charged to 100 million volts with respect to the earth. Current may oscilate up to 200 thousand amps in a lightning discharge. Temperature inside the stroke may reach 30 thousand degrees C (5x the temperature of the sun`s surface). A stroke starts and stops abruptly, so it contains r-f in addition to d-c. The discharge may take up to 150 milliseconds and consist of several flashes in both directions. It may include a path miles long, so it has a pretty good ionization trail for an antenna. If your antenna is struck by lightning, it is best to bypass the energy aroundb people and equipment. Medium wave stations have arc-gaps around the tower base insulators, Faraday screens between primary and secondary of tower r-f coupling transformers, and tower lighting chokes which keep both r-f and lightning out of the power mains. High frequency stations often use balanced wire lines, and these have an arc-gap from each wire to the earth at a point outside the station. VHF, UHF, and microwave stations use grounded antennas and coax. Towers which support the antenna generally have each tower leg separately grounded by a heavy cable to its own ground rod near the tower base. R-F cables and waveguide are grounded at the antenna and at least at the base of the tower. Coax nay be coiled with several turns between the tower base and the shack to discourage lightning on the outside of the coax from entry to the shack. Waveguide is solidly bonded to the tower but not usually coiled to make a lightning choke. The solid-state VHF, UHF, or microwave station often needs additional surge protection because of the difference in potential between electric service and antenna system grounds This takes the form of husky r-f chokes in each power wire to the r-f equipment. Each choke is shunted at each end to ground with a capacitor and with a voltage limiting device or devices, often MOV`s. There are ready-made brute force coil and capacitor low-pass pi-filters which need only addition of MOV`s to make them effective lightning suppressors. I made mine in an earlier time using Miller Coil Company tower lighting chokes and they worked well. You could wind 2 or 3 dozen turns of #12 or #14 insulated wire in an 8-in. dia. circle to make your own 0.1 millihenry chokes. The standard choke used to be 2.5 millihenry, but it is not critical. The same wiring techniques required for noise reduction apply to the biggest noise of all, lightning. Best regards, Richard Harrison, KB5WZI An interesting fact that many don't know is that lightning actually strkes upwards as the clouds are negatively charged. -- Woody harrogate2 at ntlworld dot com |
Thierry wrote:
SNIPPED HI, Good to read : http://www.astrosurf.org/lombry/qsl-...protection.htm Personnaly, in my humble opinion, under thundery weather there is no better solution than unpluging all electronic devices... Thierry, ON4SKY Agree! But, I still lost an ICOM 756 Pro II when disconnected from antenna, and had the power supply unplugged. A ground loop in the external ground on the 756 and the power supply, where 12 volt return is tied to chassis, caused damage to the power connector on the 756 and fried the 756 internal cabling and circuit boards were carbonized. I'm still waiting for my insurance settlement. MORAL: Lightning does what lightning does! |
Interesting, You made me look. (made me Look up coherer, that is).
An invention of Sir Oliver Lodge for detecting rf. Your idea of using it as a lightning protection device seems to be a misapplication. But like I said, until now, I never heard of it. "John Smith" wrote in message ... For a receiving antenna, a coherer provides excellent lightning protection. Unfortuantly, on a transmitting antenna, the rf would immediately make the coherer conductive and a direct short to ground (perhaps very low QRP power could be used?) One can easily be construted with a bottle filled with metal filings, two bare wires are inserted into the filings (not touching and seperated by a substantial amount of the filings), one wire goes to a good earth ground, the other to the antenna. If the coherer shorts to ground it only needs to be shaken to reset (I would suspect in a real lightning strike the metal would be fused, quite possibly even vaporized.) John "Jerseyj" wrote in message ... Hi all, For years I lived in an apartment and just had antenna's in the attic , but now having moved to a house in a few months I'll be putting up a 10-160 wire type antenna in my trees. Given the recent spate of serious thunderstorms, and the accompanying lightning, I'm a bit concerned about properly grouding the antenna so that I don't fry the house *smile*. I know about some articles on the ARRL site, but was wondering if anyone else had some ideas or pointers on how to practically do this ? Jerry |
"Ham op" wrote in message ... Thierry wrote: SNIPPED HI, Good to read : http://www.astrosurf.org/lombry/qsl-...protection.htm Personnaly, in my humble opinion, under thundery weather there is no better solution than unpluging all electronic devices... Thierry, ON4SKY Agree! But, I still lost an ICOM 756 Pro II when disconnected from antenna, and had the power supply unplugged. A ground loop in the external ground on the 756 and the power supply, where 12 volt return is tied to chassis, caused damage to the power connector on the 756 and fried the 756 internal cabling and circuit boards were carbonized. I'm still waiting for my insurance settlement. MORAL: Lightning does what lightning does! For sure, as soon as there is a sink, a path of lower resistance, the lightning will find it and will follow it to your most expensive accessory.. This canal can be the coaxial, the house cabling system, even yourself if by mistake you touch a metallic device during the thunder. Even the ground as state in my article can be an excellent way for the lightning to strike your installation. Hence it is better to entrust this installation to experts. So I when I say to unplug all devices, this is *all* cabling system, including grouding. Usually the insurance do an excellent job and you should be able to rebuy all your defective devices. Good luck. 73 Thierry, ON4SKY |
Does anyone know of cases where houses have fried as a consequence of
ham wire antennas, "protected" or otherwise? We all know of cases where electronics gets zapped but Jerry is concerned about his house. Be interesting to hear of actual cases, wouldn't it? Statistics would be even better, but I won't hold my breath. Chuck Jerseyj wrote: Hi all, For years I lived in an apartment and just had antenna's in the attic , but now having moved to a house in a few months I'll be putting up a 10-160 wire type antenna in my trees. Given the recent spate of serious thunderstorms, and the accompanying lightning, I'm a bit concerned about properly grouding the antenna so that I don't fry the house *smile*. I know about some articles on the ARRL site, but was wondering if anyone else had some ideas or pointers on how to practically do this ? Jerry |
Chuck wrote:
"We all know of cases where electronics gets zapped but Jerry is concerned about his house." Ben Franklin promoted lightning rods to protect people and houses before electronics was. These rods would not have sold had they not seemed to work. Tell me a drowning man will grasp at straws! Best regards, Richard Harrison, KB5WZI |
Chuck wrote:
"We all know of cases where electronics gets zapped but Jerry is concerned about his house." I`ve worked in many protected structures struck repeatedly by lightning to their air terminals, rods, and towersm resulting in not one scintilla of damage to occupants or equipment. Transportation vehicles are struck by lightning every day and seldom experience anything inside. An open convertible is not safe in a lightning strike however. Best regards, Richard Harrison, KB5WZI |
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Richard, we both know that a transportation vehicle makes a pretty good
Faraday[sp?] Cage. Lightning attaching to a wire will instantly vaporize the wire. Physical damage is generally caused by direct strike. The energy in the action intergral [I^2*R*dt] generates local heat. The thermal shock causes the damage. [And fire]. Richard Harrison wrote: Chuck wrote: "We all know of cases where electronics gets zapped but Jerry is concerned about his house." I`ve worked in many protected structures struck repeatedly by lightning to their air terminals, rods, and towersm resulting in not one scintilla of damage to occupants or equipment. Transportation vehicles are struck by lightning every day and seldom experience anything inside. An open convertible is not safe in a lightning strike however. Best regards, Richard Harrison, KB5WZI |
I had the experience of a direct hit to my antenna. It was a 130 foot cage
fed with ladderline. Coax was used the last 20 feet to bring it into the house. Inside I had a TS-440, a TS-820 and an MFJ 989C. The bolt destroyed the side of the antenna that went to the shield of the coax, the largest remaining piece was about 3" in length with most of it vaporized. The ladderline was vaporized, the other half of the dipole was untouched. The coax split open like a hotdog put in a microwave. The same stroke went into the electric utilities and blew every electronic device in the house except a cheap GE clock radio. A stroke went through the wiring in the ceiling and the explosive expansion of hot air blew all the vinyl siding off the front and one side of the house. The only fire damage was a small burn mark on the shack carpet where the coax laid on the floor. All antennas were grounded via the antenna switch and all ham gear was unplugged. All antennas had blitzbuggs and coiled coax before entering the house. These were tied to both RF ground and the single point electrical ground. What was strange was the stroke following paths along wood beams while ignoring good conducting copper wires 3 feet away. The only damage to the ham gear was a burn mark and heat distortion on the rear panel of the tuner. It's operation was unaffected. "chuck" wrote in message ink.net... Does anyone know of cases where houses have fried as a consequence of ham wire antennas, "protected" or otherwise? We all know of cases where electronics gets zapped but Jerry is concerned about his house. Be interesting to hear of actual cases, wouldn't it? Statistics would be even better, but I won't hold my breath. Chuck Jerseyj wrote: Hi all, For years I lived in an apartment and just had antenna's in the attic , but now having moved to a house in a few months I'll be putting up a 10-160 wire type antenna in my trees. Given the recent spate of serious thunderstorms, and the accompanying lightning, I'm a bit concerned about properly grouding the antenna so that I don't fry the house *smile*. I know about some articles on the ARRL site, but was wondering if anyone else had some ideas or pointers on how to practically do this ? Jerry |
Ham Op wrote:
"Physical damage is generally caused by direct strikes." Lightning can produce awsome distruction from its millions of volts and thousands of amps. Stories about it are informative, amusing, and abundant. Damage is mostly avoidable. High towers are nearly certain to be struck repeatedly in passing thunderstotms. I`ve worked in medium wave broadcasting, Short wave broadcasting, land-mobile radio, aircraft radio, and microwave relay systems aplenty. I worked decades with a worldwide corporation that had towers across the U.S.A. and several other countries in the world. That corporation had its many towers fitted with inverted Copperweld ground rods at the top to serve as lightning rods to take most of the hits the towers received. At their bottoms, the towers` lightning energy was shunted off to the earth through ground rods driven into the soil around the towers. It worked. There was no vaporized coax, tower lighting wires, or anything else. We had to operate perpetually. We couldn`t pull the switch and throw the coax out the window, even if someone were on hand to do so. Evidence of lightnong strikes were the small pits it made in the lightning rods. Best regards, Richard Harrison, KB5WZI |
Jerry wrote:
"I`m having trouble visualizing doing this grounding without affecting antenna performance." Shortwave radio antennas I`ve used were all made from Copperweld wire to withstand lightning and weather. Also, copper wire can stretch and fatigue. Copperweld`s steel core prevents this. Signal Corps rhombic kits use (3) No.12 Copperweld wires twisted together to make a cable used for antenna and transmission line. A special Wihd Turbine Company insulator is included to space the line for 600-ohm impedance. These bolt atop short tower secttons used as transmission line supports. Unless military surplus is available, substitutions would be necessary. But, open-wire line is rugged and withstands the challenges. Pick a place outside your shack to drive ground rods to serve as a ground bed for your antenna system to dump your lightning strikes to. Place the rods at about the length of your ground rods away from each other. The more rods, the better. Cost will prevent too many rods. Interconnect all the ground rods and connect this ground system to your electric service ground system. It`s the law in most jurisdictions. Run your open-wire line from your antenna to a point above your ground bed. You need arc-gaps between each transmission line cable and the earth. Form copper vees to make arc-gaps. The vertex of one Vee is going to face another to make a pair. Connect one Vee firectly to the earth. Connect the other of the pair directly to the transmission line cable. Do the sane for the other transmission line cable. When the gaps are completed, adjust the space between them until they flash over from your transmitter power, then back off until they just don`t flash over. You should now be ready for lightning on the transmission line. Connect your ladder line, twin lead, coax or whatever you will use to complete the connection to your radio to your open-wire line here above your ground bed. Isolate the radio from the powerline through a brute-force filter with MOV`s added for lightning suppression. Audio, control, and any other wires connected to the radio also need filters with MOV`s added but the current carrying capacity of the filters can be lower than that required for the power wires in most cases. A common ground point is required for all these filters. If you don`t use coax somewhere between your radio and antenna, you will lose some of the protection it provides. Its close internal spacing couples its conductors tightly. We found even solid-state receiver front-ends weren`t endangered by lightning because of grounded antennas and the coax. It would flash over before it let lightning through. Best regards, Richard Harrison, KB5WZI |
Lightning attaching to a wire will instantly vaporize the wire.
Not always. Depends on the resistance of the ground connection. If the resistance is low, a # 6 wire can take a direct strike, and barely warm up at all. Even a #10 is ok, if the connection to ground is good. You might see a tiny pit where the point of contact was. But a high resistance ground connection, and yes, it will fry. I've taken two direct strikes on my mast, and can see no damage at all. You can see a tiny pit where the strike connected to the mast top, but even it could be easily missed. According to my experience, I think the quality of the ground connection also effects the sound of the strike, not counting the sonic boom overhead. A strike hitting my mast is very quiet. It's like a light bulb being thrown on the ground, "plink", and you hear the overhead sonic boom. But when it hits the trees with their high resistance to ground, the strike is earsplitting. "CRACK-BAAAAAMMMM". :( Thats the "local" sound, not the sonic boom, although they mix. I don't operate during storms, and doubt I would, even if I could. I unplug the antennas, and ground them out to ground outside the window. If I *had* to operate during a storm, I would use my attic dipole. It's the least likely to take a hit, in general. MK |
Richard Harrison wrote:
Chuck wrote: "We all know of cases where electronics gets zapped but Jerry is concerned about his house." I`ve worked in many protected structures struck repeatedly by lightning to their air terminals, rods, and towersm resulting in not one scintilla of damage to occupants or equipment. Transportation vehicles are struck by lightning every day and seldom experience anything inside. An open convertible is not safe in a lightning strike however. The occasional stain on the seat tho' 8^) - Mike KB3EIA - |
Hal:
Actually, I have used the coherer on receiving antennas, in a couple of lightning storms it has indeed shorted to ground and needed to be shaken to restore the signals from the antenna (NOTHING near a direct hit and this is central cal, not much lightning and of little significance.) Presently, I use MOV's... at best, -=maybe=-, better than nothing... John "Hal Rosser" wrote in message .. . Interesting, You made me look. (made me Look up coherer, that is). An invention of Sir Oliver Lodge for detecting rf. Your idea of using it as a lightning protection device seems to be a misapplication. But like I said, until now, I never heard of it. "John Smith" wrote in message ... For a receiving antenna, a coherer provides excellent lightning protection. Unfortuantly, on a transmitting antenna, the rf would immediately make the coherer conductive and a direct short to ground (perhaps very low QRP power could be used?) One can easily be construted with a bottle filled with metal filings, two bare wires are inserted into the filings (not touching and seperated by a substantial amount of the filings), one wire goes to a good earth ground, the other to the antenna. If the coherer shorts to ground it only needs to be shaken to reset (I would suspect in a real lightning strike the metal would be fused, quite possibly even vaporized.) John "Jerseyj" wrote in message ... Hi all, For years I lived in an apartment and just had antenna's in the attic , but now having moved to a house in a few months I'll be putting up a 10-160 wire type antenna in my trees. Given the recent spate of serious thunderstorms, and the accompanying lightning, I'm a bit concerned about properly grouding the antenna so that I don't fry the house *smile*. I know about some articles on the ARRL site, but was wondering if anyone else had some ideas or pointers on how to practically do this ? Jerry |
Jerry - I'll second that idea. I use banana plugs on the balanced feedline
from my inverted V wire antenna. If the weather looks like it might get bad, I just unplug it from my transmatch and throw it out the window (the feedline - not the transmatch!) Warren KC8YKQ Bob Miller wrote in : I have a 10-80 wire connected between 3 trees. It's fed with ladderline. Lightning protection is simple -- with banana plugs and jacks, I can unplug the ladderline just outside the window whenever it looks rainy. |
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